This invention relates to method of managing a communications interface, such as a frame relay interface.
Frame relay is a technology for access to wide area networks. The frame relay protocol operates at a sublayer of the data link layer, which provides the minimum functionality needed to take advantage of the statistical properties of the communication. Unlike preexisting protocol suites in use in general topology subnetworks, it also performs relaying, and multiplexing at this sublayer. Other data link layer functions are provided only in systems connected to the edges of the frame relay subnetwork.
Frame Relay presently uses ANSI T1.617 Annex D which is herein incorporated by reference, or the very similar CCITT Q.933 Annex A protocol, to provide the status signaling protocol requirements between Frame Relay devices.
The Newbridge Networks Corporation Mainstreet.RTM. 36120 switch is a single unit frame switch, with ports providing the correct status signaling protocol to external devices. In particular, it can include FRE (Frame Relay Engine) cards via a wiring hub known as a FASTbus. The FRE card is a multi-processor card with a 68340 general purpose control processor and two 68EC040 processors used for frame switching and I/O.
There is a need to provide status signaling between FREs in addition to external Frame Relay devices.
Annex D cannot maintain the status of the required number of inter-FRE 36120 connections due to its close coupling with management frame size; elements which describe the present signaling status of all connections on a link must fit inside of a single frame. Since the FASTBus is based on FDDI technology and is therefore limited to a maximum frame size of 4500 octets, this also limits the number of information elements per frame.
Annex D also provides for an `Asynchronous STATus` message frame, which allows a Frame Relay device to inform its connected device of a change in signaling status outside of the normal, regular interval poll and response messaging. One management frame must be used for each connection's change of state. Unfortunately, a simultaneous change in the state of a link with multiple connections can result in hundreds of management frames being exchanged.
An object of the invention is to overcome this problem.